1. Field of Invention
The instant invention relates to a novel method and means for the efficient, safe, and economic decontamination of entire physical structures, such as buildings, and/or articles contaminated by microorganisms inclusive of pathogenic spores.
2. Prior Art
The prior art of eradication of entire buildings of insects such as termites, cockroaches, wood-boring beetles, rats, mice, bats and other such arthropod and vertebrate animals has, over the last approximately sixty years, consisted of covering and sealing the structure to be treated with a vinyl tarpaulin and, thereafter, introducing the selected fumigant into the structure covered by or confined within the tarpaulin. Among the various fumigants used in the prior art for this purpose has been methyl bromide, a USEPA registered pesticide. However, due to the ozone-depleting properties of methyl bromide as have been recognized by the Montreal Protocol of 1992, methyl bromide was officially added to the list of ozone-depleting chemicals and, pursuant thereto, its production was frozen at 1991 levels thereof. Further, any chemical with an ozone depletion potential (ODP) of greater than 0.02 was, under the Protocol, banned at the end of 2000 and, in the case of methyl bromide, its use in the United States has been banned by the Environmental Protection Agency (xe2x80x9cEPAxe2x80x9d) effective in 2005. Moreover, neither methyl bromide nor other known structural fumigants, have ever been employed for the purpose of decontamination of a structure which are contaminated by microorganisms that are pathogenic to humans including bacteria (prokaryota).
Methyl bromide has been used as a fumigant since the 1930s to control pests in soil, stored commodities, structures and shipments that must meet agricultural quarantine regulations. The major use in agriculture is soil fumigation. It is an extremely effective herbicide, nematicide, insecticide, and fungicide. It is important for the large-scale commercial production of strawberries, tomatoes, peppers, melons, grapes, cucumbers, eggplants, ornamentals, and tobacco. In addition, U.S. regulations require that a wide array of imported food and non-food commodities be fumigated with methyl bromide as a condition of entry into the country. Methyl bromide has never been employed as a means for decontamination of structures of human pathogens such as viruses and hazardous bacteria. Rather, if the contamination of a structure was known to be limited to a particular surface or article, one could employ bleach (sodium hypochlorite), a foam, such as Sandia foam, or a toxic gas, such as chlorine dioxide, which are commonly unstable and/or explosive.
Methyl bromide (CH3Br, also abbreviated as MeBr), a member of the chemical family of alkyl halides, is a colorless and non-flammable gas, which has no odor at toxic levels. It is stable under normal conditions of handling and use. Methyl bromide gas is commercially available at a purity greater than 99% from Great Lakes Chemical Corporation (West Lafayette, Ind.) under the trade name Meth-O-Gas(copyright) 100 and Meth-O-Gas(copyright) Q.Most fumigation treatments are recommended on the basis of dosage for a certain volume, expressed in pounds per 1000 cubic feet (lb/1000 ft3) in the industry, and in milligram per liter (mg/l) using the metric system. The common dosages used for treating commodities range from 1 lb/1000 ft3 for dried fruits such as dried apples and prunes, to 8 lb/1000 ft3 for cotton seeds, equivalent of from 16 to 128 mg/l. For structural fumigations, such as in termite infested houses and buildings, the common dosage is from 1 to 3 lb/1000 ft3, equivalent of from 16 to 48 mg/l. An important factor used in the industry is the amount of gas acting on the pests over a certain period of time, expressed as the product of concentration and time (CT product, mg-hr/l). The use of methyl bromide has never been considered at the concentration, temperature, and time combinations suggested herein.
Given the new reality of bio-terrorism and its potential in the wake of the events of September, 2001, much concern and attention have been directed to the decontamination of entire buildings that have been the subject of a biological attack such as occurred in Florida, Washington, D.C., and various U.S. Post Offices in New York, New Jersey, Connecticut and elsewhere. Government, inclusive of the EPA and CDC, as well as research community and industry have lacked experiences other than that of decontaminating buildings subjected to a purely chemical contamination, such as by asbestos or PCBs and therein has had no experience with the many problems related to the decontamination of entire buildings, parts of which have been infected (or potentially infected) by a bio-weapon consisting of a microorganism such as a virus, bacteria or spores thereof. Historically, structural decontaminations of biological weapons occurred at an Army facility at Ford Detrick in 1970 and 1971 for a building previously used for producing Bacillus anthracis, commonly known as anthrax. The building was decontaminated twice using formaldehyde gas, and further hydrochloric acid was forced through pipes and valves that carried a bacteria mixture. Anthrax spores and other bacteria were not found after the decontamination. However, the damage by the caustic decontamination has threatened the structural integrity of the building. In light thereof, the EPA and CDC, after consultation with scientists, public health specialists, industry experts and even historians on the subject of bio-weapons, settled on the use of chlorine dioxide gas on a massive scale, never before attempted, as a means of decontaminating buildings exposed to a bio-weapon and, particularly, spores of anthrax. As such, operating with little historical or scientific precedent, EPA/CDC have attempted to employ, in substantial quantity, chlorine dioxide gas which, in the past, had been employed only in context of purification of drinking water. In these efforts, the EPA determined that use of chlorine dioxide gas on a large scale entails several hazards and problems, this apart from an underlying question with regard to the concentration, temperature, humidity and time of exposure necessary to kill anthrax spores in sufficient quantity. For example, the humidity within a building to be so decontaminated must be first be elevated from an ambient level of about thirty percent to that of seventy percent, which is considered the optimum level for chlorine gas to kill spores of anthrax. Furthermore, because of the extreme oxidative properties of chlorine dioxide, substantially all equipment and furniture, within a building to be decontaminated must be removed to preclude corrosion or degradation of the surfaces thereof by the oxidative effect of the chlorine dioxide. Further, a special chemical, such as sodium bisulfate, must be employed to neutralize and vent the chlorine dioxide from the building itself. Then, all removed equipment and furniture must be brought back into the building after being fumigated in chambers with flammable ethylene oxide gas. Thereafter, test strips containing a bacterial endospore (Bacillus subtilis var. niger) more chemically resistant than anthrax spores are used to verify the effectiveness of the chlorine dioxide decontamination.
In view of the above, an urgent need has arisen for a method of decontamination of whole buildings (including the inside, outside, duct work and piping therein,) that will not only obviate the need to remove sensitive articles such as photographs, documents, and computers, and heavy items such as furniture, but which will also obviate the need to pump steam into the structure to elevate the humidity thereof and that does not require a special chemical to neutralize the active agent beyond these issues is a need for a method that can provide a higher level of confidence that the targeted pathogenic organism has, in fact, been killed, and therefore is unable to germinate.
In spore-forming bacteria, the spore is protected from environmental extremes of drought and temperature by a coat made of numerous cross-linked proteins (Driks, A. 1999. Bacillus subtillis spore coat. Microbiol Molec. Biol. Rev. 63:1-20). It has been determined that spore coats or shells exhibit a considerable degree of uniformity in their chemical linkages, such that the shell of one spore is substantially similar in chemical structure to the shell of other spores and, in particular, spores of Bacillus which is the genus of a species of bacteria, namely, B. subtilis var niger, employed as the test bacteria upon test strips, that has become a universally accepted standard for determination of whether a bacterial spore has been killed by a treating agent or method. These spores and bacteria are also used to test the efficacy of treatments for killing B. anthracis. 
The instant invention therefore addresses the need for a more reliable, comprehensive, convenient, and cost-effective method of decontamination of entire structures and their contents that have been contaminated, or potentially contaminated with pathogenic microbes including, without limitation, anthrax and spores thereof.
The present invention comprises methods of using methyl bromide as an anti-microbial agent in the decontamination of whole structures or articles that have been contaminated, or may be contaminated, with microorganisms such as bacterial spores. This invention is based on a new use of methyl bromide, a non-flammable, non-corrosive, and E.P.A. registered pesticide. The instant method entails the gas-tight sealing of the entire building to be decontaminated under tarpaulins or other equivalent means. After the building is sealed, a sufficient amount of methyl bromide gas is introduced within the seal so that methyl bromide diffuses into all parts of the building, its surfaces and articles therein. The sealed structure is maintained with the concentration of methyl bromide at a sufficient temperature for a sufficient period of time. This process renders pathogenic bacterial spores in or associated with the structure or its contents nonviable so that germination will not occur when the spore is exposed to a favorable environment for germination. The method further comprises a step of unsealing and aerating decontaminated structure to aerate the methyl bromide gas, without requirement for any special purpose cleaning or deactivation agent, either in gaseous form mixed with air, or as a scrubbing procedure following the fumigation.
The application of methyl bromide using the method of the present invention, at temperature greater than 20xc2x0 C., preferably greater than 25xc2x0 C., and with a concentration of methyl bromide about 200 mg/l and above, and an exposure time greater than 30 hours, prevents germination of B. subtilis var. niger and B. stearothermophilus spores. In additional field testing, the application of methyl bromide using the method of the present invention, at temperature between 28xc2x0 C. and 38xc2x0 C., and with a concentration of methyl bromide about 250 to 350 mg/l, and an exposure time of approximately 48 hours, also prevents germination of these spores. The method of the present invention provides a marked improvement in coverage, level of confidence, and cost-effectiveness of result over existing methods of structural microbial decontamination.
It is accordingly an object of the invention to provide an improved method of whole structure decontamination for pathogenic microbes.
It is another object to provide a method of the above type, which does not require the removal of all contents of a structure to be decontaminated or the elevation of the humidity, therein.
It is a further object of the invention to provide a method of structural decontamination for pathogenic spores without subjecting the interior of a building as so treated to oxidative agents or requiring the use of special cleaning agents to effect removal of the treating agent at the end of the process.
It is a still further object to provide a method of the above type to more cost-effectively, safely and reliably decontaminate a structure of microbial pathogens including, without limitation, Bacillus anthracis spores.
It is another object to provide a method of the above type comprising a use of methyl bromide as a decontaminating agent for bacteria and their spores.
It is a still further object of the invention to provide a method of the above type in which the effectiveness thereof may be authoratively ascertained through the use of test strips containing bacteria of a type more resistant to heat and toxic chemicals than B. anthracis and which are universally accepted as a measure of the effectiveness of microbial decontamination.
It is a yet further object to provide a method of the above type employing long established procedures for fumigation of structures for the control of arthropod and vertebrate pest animals, however, only substituting the use of methyl bromide in its inventive parameters of use, in lieu of existing fumigants.
It is yet another object of the invention to use a chemical for decontaminating B. anthracis and its spores which is non-flammable and stable.
It is still another object of the invention to provide a method of the above type comprising a use of methyl bromide as a decontaminating agent for bacteria and their spores which generally does not harm electronic equipment or sensitive materials which might be damaged by a strong oxidizing agent
It is yet another object of the invention to provide a method of the above type that allows for an unlimited volume for treating areas.
The above and yet other objects and advantages of the present invention will become apparent from the hereinafter set forth Brief Description of the Drawings and Detailed Description of the Invention.